Heat exchanger



Nov. 5, 1957 I RQR. THOMPSON 2,312,164

HEAT EXCHANGER Filed Sept. 17, 1955 30 INVENTOR HEAT EXCHANGER RichardR. Thompson, East Rocltaway, N. Y., assignor to The Lummns Company, NewYork, N. Y., a corporation of Delaware 7 a Application September 17,1953, Serial No. 380,844

' 2 Claims. (Cl. 257-32) This invention relates to improvements in heatexchangers of the shell-and-tube type and more particularly to thoseemployed for heating boiler feed water by circulating the water throughthe tubes and passing steam into the shell and around the tubes. Incertain high pressure heaters of this type the space within the shell isdivided into a condensing zone, a steam desuperheating zone and v meansfor minimizing heat exchange between said side- .by-side zones; and toprovide means for effectually excluding, from the desuperheating zone,condensate formed in the condensing zone.

. Further objects and advantages of the invention will appear from thefollowing description taken in connection 1 with the accompanyingdrawings. In the drawings? a Fig. 1 is a vertical sectional view, partlybroken away,

of a feed water heater embodying the invention.

Fig. 2 is a horizontal sectional view on the line 22 of-Fig.- l. p H

Fig 3 is a horizontal sectional view on the line 3-3 of Fig.1. i Theinvention is shown embodied in a feed water heater having anelongatedshell, vertically arranged, and a header orchannel 2 at its lower end.The structure of the channel includes a tube sheet 3. A bundle of U-s'li-aped tubes"'4 extends from the'tube sheet upward through the shellfor most of the height of the latter. The channel 2 has a water inletnozzle 5 and a water outlet nozzle 6. These nozzles are shown atdiametrically opposite sides of the channel 2 but they can be otherwisesuitably oriented. A removable closure 7 forms the lower wall of thechannel and is shown held in closed position by locking and sealingmeans 8, such as that shown in U. S. Patent No. 2,268,507 of Gertzon.Other suitable locking and sealing means may be employed, however. Thespace within the channel is divided by a pass partition structure 9 intoa compartment 10 communicating with the inlet nozzle 5 and a compartment11 communieating with the outlet nozzle 6. Compartment 10 communicateswith one leg 4a of the U-tubes 4, and compartment 11 communicates withthe other leg 4b of said tubes. Hereinafter, in the specification andclaims, the legs 4a and 4b will, for convenience, be referred to astubes, and in the claims, such term is intended to include either thelegs of U-tubes or separate tubes, which may be connected to returnheader means other than the bends of the tubes.

The shell 1 is formed in upper and lower sections 1a and 1b,respectively, flanged and bolted together, as at 12. At the lower endthereof, shell section 1b is welded to the tube sheet portion of thechannel 2, as at 13. Within the lower shell section there is a verticaldiametrically disposed partition 14 extending upward from the tube sheet3 to a point near the upper end of said section. At its upper end, saidpartition is formed with a welded-on bafile portion 15 extendinglaterally outward and terminating short of the adjacent wall of theshell section 1b. Along its outer edge said baflie portion has anupstandinglip 16 forming a dam. As shown, the partition, including its'bafile portion, is formed of two walls spaced apart to form a dead airspace therebetween, for heat insulation. Said walls and the lip 16 arewelded along their opposite edges to the shell section 1a and the loweredgesof the walls are welded therealong to the tube sheet 3. Thepartition divides the space within the lower shell section into adesuperheating zone 17 and a condensate subcooling zone 18. All of thetubes 4a extend through the subcooling zone and all of the tubes 4bextend through the desuperheating zone, the baflie 15 being perforatedto admit the tubes 4b and all of said tubes being spaced inward of thelip 16. Near the lower end thereof the lower shell section has a steaminlet nozzle 19 opening into the desuperheating zone 17 and a condensateoutlet nozzle 20 opening from the subcooling zone 18. Within thedesuperheating zone there are transverse baffles 21 formed and arrangedto cause serpentine flow of the steam, and in the subcooling zone, thereare similar bafiies 22 to cause serpentine flow of the condensate. Thebaffle lip 16 at the top of the desuperheating zone and the adjacentportion of the shell wall define an exit 23 for the steam to an upperportion of the shell space.

A condensing zone is formed by the portion of the shell space above thedesuperheating and subcooling zones. All of the tubes of the bundleextend through this space and the bundle is provided with a series ofspaced transverse baffles 24. Desirably, these baflles include theentire cross section of the bundle. At the side thereof, over thedesuperheating zone, the battles are cut away to provide' openings 25for upward passage of the steam and have an upturned edge forming adam26. At the opposite side thereof the baffles are cut away to provideopenings 27 permitting the condensate to spill therefrom into thesubcooling zone 18. The lower shell section 1b has a condensate baffle28 in the form of a gutter located in a position spaced above the steamexit 23 of the desuperheating zone. The gutter extends around the innerWall of the shell to catch condensate draining therefrom and has openends disposed over the subcooling zone to spill the condensate into saidzone. The lower shell section also has a nozzle 29 near the upper endthereof and disposed to deliver to the subcooling zone drips orcondensate from other parts of a power plant system in which the feedwater heater is used.

At the top of the shell 1 there is an air vent 3t) and adjacent theupper end of the tube bundle there are two staggered baffles 31 betweenwhich any air in the heater passes to the vent.

In the operation of the heater, boiler feed water to be heated entersthe channel compartment 10 through the nozzle 5, flows upward throughthe tubes 4a which extend through the subcooling and condensing zones,and downward through the tubes 4b which extend through the condensingand desuperheating zones. Thence, the water flows out of the heaterthrough channel compartment 11 and outlet nozzle 6. Steam enters thedesuperheating zone 17 through the nozzle 19 and the desuperheated steampasses upward through the exit 23 of said zone into the condensing zoneand into contact with the upper portions of the tubes 4a and 4b, and iscondensed thereon. The steam ascends through the bafiie openings 25 andis directed in transverse parallel streams by the baflles 24, Y

for good contact with the tubes. Substantially all of the steam whichremains uncondensed above the series of baffles 24 will be condensed onthe upper end portion of the t ube' bundle, and air and any remainingsteainescapes through the vent 30. i

The steam condensate Talling from the tubesonto the baflles 24 isconstrained by the dams 26 to flow off the opposite side of the bafflesoverlying the subcooling zone 18 and falls through the openings'27tosaid zone. Any condensate collecting on the bafiie top 15 of thedesuperheating zone is shed to the subcooling zone, and condensatedraining down the shell wall above steam exit 23 of the desuperheatingzone is'interceptedby the gutter and diverted to the subcooling zone.The baffles 15, 24 and 28 thus cooperate .to'exclude condensate from thedesuperheating zone. The condensate is subcooled in the zone 18 by' thecoldest portion of the tubes 4b and is drawn off through the nozzleZO,the rate of withdrawal being such as to maintain a desired level of thecondensate within said zone. In starting up the operation of the heater,any condensate formed in the desuperheating zone maybe drained offthrough a normally closed passage 32 in the tube sheet. After operation,the subcooling zone may be drained through a normally closed passage 33in the tube sheet.

The design and arrangement of the heater provides for counter-flow ofthe feed water and the steam in the desuperheating zone and forcounter-flow of the feed water and the condensate in the subcoolingzone. Side-by-side arrangement of the hottest and coldest zones of theheater with minimum heat exchange therebetween is rendered possible bythe heat-insulating partition 14 and undesired submergence of tubesurface is avoided. All the tube surface is rendered available for heatexchange purposes in a proper manner, with consequent substantialincrease in heat transfer efficiency.

Access to the interior of the shell is had for servicing or repair byunbolting and removing the upper section of the shell. Since all of thenozzles for outside connections are borne by the channel and the lowersection of the shell, there are no outside connections to be broken forthe removal of the upper section of the shell.

While a very satisfactory form of the invention is disclosed, it will beunderstood that the disclosure is illustrative and not limiting and thatthe invention comprehends such modifications as will come within thescope of the following claims.

I claim:

1. A heat exchanger comprising an elongated vertical- Iy-disposed shellhaving a steam inlet and a condensate outlet, a plurality of tubesextending vertically within said shell, a tube sheet closing the lowerend of said shell, means for circulating a fluid to be heated upwardlythrough a first leg of said tubes and thence downwardly through a secondleg of said tubes and including a fluid directing channel structure atthe lower end of said tubes associated with said tube sheet, means fordividing the lower section of said exchanger into desuperheating andsubcooling zones, said desuperheating zone including the steam inlet andthe lower relatively hot ends of tubes of said second leg and saidsubcooling zone including the condensate outlet and the lower relativelycool ends of tubes of said first leg, said means including aheat-insulating vertical partition within said shell and between saidlegs of tubes and extending from said tube sheet to a point short of thetop of said shell and a horizontal heat-insulating partition extendingtransversely of the tubes of said second leg and having sealingengagement with the upper end of said vertical partition, saidhorizontal partition being spaced from the shell at its edge oppositesaid vertical partition whereby an opening is formed through whichdesuperheated steam may pass from said desuperheating zone, the sectionof the heat exchanger above said first mentioned zones forming acondensing zone communicating with the upper end of said desuperheatingzone through the opening formed by said horizontal partition and withthe upper end of said subcooling zone through the opening formed betweenthe upper end of said vertical partition and said shell, and bafflemeans above the opening from the desuperheating zone to directcondensate from the condensing zone away from the desuperheating zoneand into the subcooling zone.

2. A heat exchanger as claimed in claim 1, wherein the natile meansabove the desuperheating zone includes the horizontal heat-insulatingpartition and a gutter battle above the opening formed by the shell walland said horizontal partition and positioned to catch condensatedraining down the shell wall, divert it from said opening and direct itto said subcooling zone, said opening being arranged so that none of thetubes pass therethrough.

References Cited in the file of this patent UNITED STATES PATENTS1,640,746 Braun Aug. 30, 1927 2,259,604 Banks Oct 21, 1941 2,299,455Bowman et al Oct. 20, 1942 2,412,573 Fraser Dec. 17, 1946 2,489,944 Wornet al Nov. 29, 1949 2,661,190 Kirkpatrick Dec. 1, 1953 2,666,625 ByerleyJan. 19, 1954 2,723,109 Kirkpatrick Nov. 8, 1955

